Method and device for making a composite plate

ABSTRACT

A process for manufacturing composite sheets includes steps of:
         continuously depositing a web of yarns, in the form of a mat of continuous yarns, a woven, a knit or an assembly of continuous non-interlaced yarns on a moving substrate;
           depositing a powder of an organic material capable of forming a coating layer under the action of heat on at least one side of said web;   heating the web coated with the powder to a temperature sufficient to melt the powder;   compressing and cooling the web so as to form a composite strip; and   cutting the strip in the form of sheets or winding the strip up on a rotating support.

This application is a 371(c) of PCT/FR03/03648, filed on Dec. 10, 2003,which claims priority to French application number 02/16043, filed onDec. 13, 2002, the text of which is herein incorporated by reference.

The present invention relates to a process and to an installation forthe continuous manufacture of a composite sheet comprising athermoplastic or thermosetting matrix and reinforcing yarns, and a layerof a coating that improves the surface appearance, this sheet being moreparticularly intended for the production of panels for vehicles orcontainers for transporting or storing merchandise.

BACKGROUND OF THE INVENTION

More precisely, the invention relates to a process, and to theinstallation allowing its implementation, which consists in applying, toa web of yarns continuously deposited on a moving substrate, a powder ofa material capable of reacting under the effect of heat in order to forma coating layer, said web comprising at least one organic, thermoplasticor thermosetting, material and at least one reinforcing material, and inheating and then compressing the assembly thus obtained in order to forma composite sheet.

The walls of trucks, trailers and containers used for transporting orstoring merchandise are formed from panels generally consisting of athermoplastic or thermosetting material into which reinforcing yarns,especially glass yarns, are incorporated, and of a topcoat whosefunction is to improve the appearance of the surface visible from theoutside. The main purpose of the topcoat is to attenuate the “marking”effect due to the presence of the reinforcing yarns near the surface, inother words to make it smoother and possibly glossier. The estheticappearance is not the only advantage provided by the coat: since thesurface finish is improved, it becomes easier to apply patterns andinscriptions, for example by means of a paint or in the form ofstickers, or to maintain the state of cleanliness thereof.

The walls of trucks, trailers and containers each consist of a one-piecepanel of large dimensions, possibly up to 3.5 meters in width and 17meters in length, or even more.

Several known methods are used to manufacture these panels.

A first method consists in forming a continuous strip from a matrixcomprising reinforcing yarns, in coating this strip with a film capableof forming the coating layer and in cutting said strip to the requireddimensions in order to form the final composite panel.

To obtain very wide panels requires the use of a film at least as wideas that of the panel. It is difficult and also very expensive to producesuch films, as the production requires machines that are speciallyadapted to these large widths. The film may be obtained and depositeddirectly by extrusion at the time of manufacture of the panel or thefilm may be provided already wound in the form of reels. For widthsgreater than 2 meters, it is not conceivable to use extrusion since thecost of the machine is much too high.

With reels, there are additional problems associated with production(size of the reels, quality of the film), with storage and with therequirement to have a specific film for each type of panel, especiallyas regards the color. Conventionally, these drawbacks are alleviated byusing several films of smaller width that are juxtaposed or partiallyoverlapped at the edges in order to be matched to the size of the panel.However, the final panel is unsatisfactory as marks remain visible wherethe films are joined together.

Another method consists in cutting the strip from the abovementionedfirst method to the dimensions of the panel and then in applying thecoating in paint form.

The nature of the material used does not allow correct bonding of thepaint when it is applied directly. It is for this reason that it isgenerally recommended to pretreat the surface to be coated, for exampleby applying an adhesion primer or else to carry out a flame treatment(“flame brushing”) or a corona treatment. It is general practice toapply a layer of a “lining” primer to the treated surface, said primerhaving the consistency of a mastic and serving to mask the surfaceirregularities. The coat of paint that forms the actual topcoat isapplied to the primer, possibly after a rubbing-down step.

Although this method allows great freedom in the choice of color, italso has drawbacks. Its implementation requires a painting booth capableof taking large panels, and also having to be equipped with means forthe completely safe use of paints based on organic solvents that areundesirable both for users and for the environment, and for keeping thepanels free of dust.

The above process is a discontinuous process in which each panel istreated individually in a relatively long treatment cycle: to give anexample, with the adhesion primer, several hours of drying are neededbefore the next layers can be applied.

It is an object of the present invention to provide a process thatallows rapid and continuous manufacture of composite sheets which have acoating improving the surface appearance and are of large dimensions,especially a large width.

It is also an object of the present invention to provide a process inwhich the coating is formed on the composite sheet by applying a powder.

SUMMARY OF THE TNVENTION

These objects are achieved thanks to the process according to theinvention, which comprises at least the following steps:

-   -   a web of yarns, in the form of a mat of continuous yarns, a        woven, a knit or an assembly of continuous non-interlaced yarns,        is continuously deposited on a moving substrate, this web        comprising at least one organic material and at least one        reinforcing material;    -   a powder of an organic material capable of forming a coating        layer under the action of heat is deposited on at least one side        of said web;    -   the web coated with the powder is heated to a temperature        sufficient to melt the powder;    -   the web is compressed and cooled so as to form a composite        strip; and    -   the strip is cut in the form of sheets or wound up on a rotating        support.

The web of yarns is formed from at least one organic, thermoplastic orthermosetting, material forming the matrix and from at least onematerial capable of reinforcing said matrix.

As material that can form the matrix, mention may be made ofthermoplastics such as polyolefins, for example polyethylene andpolypropylene, polyesters, for example polyethylene terephthalate (PET)and polybutylene terephthalate (PBT), polyamides, for example nylon-6,nylon-6,6, nylon-11 or nylon-12, polyvinyl chloride (PVC) or acrylichomopolymers or copolymers, and of thermostats, such as epoxy resins,unsaturated polyester resins, polyvinyl esters or phenolic resins.

The reinforcing material may be any type of material that can beobtained in the form of yarns, for example glass, carbon or aramid.

In general, the web is formed from a reinforcing material,advantageously glass, and from one or possibly several thermoplasticorganic materials, advantageously polyethylene, polypropylene, apolyester (PET or PBT) or a polyamide, or a thermoset, advantageously anepoxy resin, an unsaturated polyester resin, a polyvinyl ester or aphenolic resin. Preferably, the web consists of glass and one or morethermoplastic organic materials.

The web generally comprises between 20 and 90% by weight of reinforcingmaterial, preferably in glass form, preferably between 30 and 85% andparticularly preferably between 40 and 80% by weight of reinforcingmaterial. It may consist completely or partly of yarns of thermoplasticmaterial and yarns of reinforcing material, these yarns preferably beingarranged alternately in the web and advantageously being intimatelymixed. The web may also include hybrid yarns obtained by joiningtogether and simultaneously winding yarns or filaments of one of thethermoplastic organic materials and of the reinforcing materials, thesehybrid yarns possibly being mixed with yarns consisting solely of onethermoplastic organic material and/or one reinforcing material. The webmay also consist completely or partly of yarns of reinforcing materialcoated with thermosetting organic material.

Preferably, the web comprises at least 50%, advantageously at least 80%and preferably 100% by weight of intermingled yarns.

The term “intermingled yarns” is understood to mean here yarns composedof glass filaments and filaments of a thermoplastic organic materialwhich are intimately intermingled. These yarns may be obtained bymechanical means, described for example in patent U.S. Pat. No.4,818,318. Under the conditions of that patent, the reinforcing yarnsand the thermoplastic yarns are paid out from their respective packagesand then the filaments constituting them are separated in the form oftwo webs of the same width. These webs are then brought into contactwith each other to form only a single web, while alternating asregularly as possible the two kinds of filaments, and then theintermingled filaments are combined into a single yarn.

The term “intermingled yarns” should also be understood to mean yarnsthat are obtained directly during manufacture of the thermoplasticorganic filaments and the glass filaments, for example as described inEP-A-0 599 695 and EP-A-0 616 055. The filaments obtained by meltextrusion and mechanical drawing of a thermoplastic organic material arethus drawn in the form of a web and are intermingled with a bundle or aweb of glass filaments (or are thrown into said bundle or said web),said glass filaments also undergoing drawing. These yarns are preferredas the distribution of the filaments is more uniform than in theintermingled yarns obtained in another manner.

According to the invention, the web of yarns is in the form of a mat ofcontinuous yarns, a woven, a knit or an assembly of continuousnon-interlaced yarns, for example a mesh or a weft-insertion warp knit.The web may comprise one or more of the abovementioned structures basedon continuous organized yarns, lying in directions that may vary widely,it being possible furthermore for these structures to be bonded togetherby various methods, for example by needle bonding, stitching-knitting bymeans of a binding or bonding yarn. According to a preferred embodiment,the web is exclusively in the form of at least one woven and/or knitand/or assembly of continuous non-interlaced yarns, at least partlyformed from intermingled yarns.

The wovens falling within the scope of the invention compriseintermingled yarns that may be warp or weft yarns, preferably both atthe same time.

The web of yarns moving at a speed of, for example, between 0.5 and 10m/min passes through a device allowing the coating material in powderform to be applied. Any known device allowing a uniform distribution ofthe powder to be obtained can be used. In particular, the web may bemade to pass through a bed of powder, the height of which at the exit isadjusted by means of a doctor blade allowing a constant thickness ofpowder to be deposited. It is also possible to use a powder coatingdevice comprising one or more rolls provided with grooves or with nips,or an electrostatic device operating by spraying the powder onto theweb, the powder particles being retained on the surface owing to thedifference in electric potential difference. When the powder coatingoperation relates to the underside of the web, it is necessary tocombine the electrostatic device with a means for heating the powderbefore it is sprayed, so that the particles adhere to the web and do notsubsequently fall off by gravity.

The thickness of the powder layer is adjusted so as to obtain a coatingon the final composite strip having a thickness of between 0.3 and 1 mm,preferably between 0.5 and 0.8 mm.

In general, the powder consists of particles of thermoplastic orthermosetting material, preferably having a high film-formingcapability. Also preferably, the powder gives the final coating anopacity sufficient to make the reinforcing filaments in the matrixinvisible.

The thermoplastic material may be chosen from polyolefins, in the formof homopolymers such as polyethylene or polypropylene, or in the form ofcopolymers, polyamides, polyesters and PVC.

The thermosetting material is selected from epoxies, polyesters,polyurethanes and phenolic compounds.

Preferably, when the powder is applied directly to the web, withoutintermediate structure as is indicated later, it is of the same natureas the matrix.

The powder may furthermore include additives, such as color pigments, UVstabilizers, anti-graffiti agents, agents for improving impact(stone-chip) resistance and scratch resistance, antifouling agents andfire retardants.

The total content of additives is generally less than 30%, andpreferably less than 10%, of the total weight of the powder.

The powder-coated web of yarns then passes through a zone in which it isheated to a temperature high enough to allow the web of yarns to beconverted into a matrix within which the reinforcing yarns are embeddedand to melt the powder into a coating film.

To be high enough, the temperature must be above the melting temperatureof the organic material having the highest melting point. Additionally,the temperature must remain below the degradation temperature of thematerial having the lowest melting point. Within the context of theinvention, the degradation temperature is the temperature at which thematerial starts to deteriorate—this deterioration may be manifested bydecomposition (ignition), loss of integrity (creep) and/or color change(yellowing).

As an example, the heating temperature may be around 100 to 300° C.,especially around 200 to 220° C. when the web consists of glass andpolypropylene and the coating is based on polypropylene.

The heating may be carried out in several ways, for example with the aidof an infrared-radiating device such as an oven, panels or lamps, withthe aid of a device that blows hot air, such as a forced-convectionoven, with the aid of a contact heating device, such as heated rolls, orelse with the aid of a double-belt laminator. The heating may combineseveral of the aforementioned means.

In many cases, it is preferable for the heating step to be followed by aconsolidation step, which consists in subjecting the assembly formed tocompression in a suitable device, for example a two-roll calender. Theforce applied depends on the nature of the yarns of the web and on therheology of the coating material—it may vary from 1 to 100 bar.

The pressure exerted in the compression device makes it possible tocompact the web of yarns and make the coating layer uniform, especiallyby giving it a constant thickness, the structure obtained then being setby cooling.

The cooling may be carried out partly during the compression, forexample by means of the rolls when maintained at a temperature below thesolidification point of the lowest-melting-point material, for examplebetween 10 and 130° C., preferably at a temperature below 80° C. andbetter still below 60° C.

The compression device may also consist of several calenders, especiallywhen the thickness is large or if it is desired to have a high degree offlatness and/or a high production rate.

To prevent the coating from adhering to the walls of the rolls, it ispreferable to cover them with a nonstick coating such as PTFE or toinsert a material having nonstick properties between the powder-coveredweb and the rolls. This material may, for example, be a film ofsiliconized paper, whether or not to be used just once, or an endlessbelt of PTFE-coated cloth.

According to one embodiment, the compression device is in the form of abelt press, the belts being made, for example, of steel, glass cloth oraramid cloth, these preferably being coated with PTFE. Preferably, thepress furthermore includes a hot zone upstream of the compressiondevice, and a cold zone downstream, the heating or cooling elementsbeing in the form of plates, bars or rolls (calenders).

As already indicated, the cooling may take place in the compressiondevice or else it may be carried out independently of the compression,for example by natural or forced convection of cold air or by passageover a cooling table.

The sheet obtained on exiting the cooling zone may be wound up on amandrel of suitable diameter depending on the thickness and thestiffness of the sheet, or it may be cut up by a cutting device, forexample a guillotine or a circular saw.

The manufacture of the composite sheet may be carried out from a singleweb as described above, which corresponds to the simplest embodiment.However, it also falls within the scope of the present invention to beable to form a sheet by combining one or more other webs of yarns ofmaterials and/or structures that differ from the previous web, for thepurpose in particular of forming thicker sheets. In this case, the websof yarns are preferably formed from wovens and/or knits and/orcontinuous non-interlaced yarns.

In general, it is possible to deposit, on at least one side of the webof yarns, before the powder is applied, other structures endowed withspecific properties. These intermediate structures give the finalcomposite sheet better characteristics, for example additionalreinforcement, and fulfil several other functions.

Firstly, they constitute a means of reducing the “marking” effect of theyarns present on the surface of the reinforced matrix, by forming anadditional layer whose thickness may be regulated according to thedesired result.

These structures also help to improve the adhesion of the coating layerto the reinforced matrix—in certain cases, the adhesion can be effectedby their agency alone.

Such structures also allow lightened composite sheets to be obtained.

Finally, they produce a “barrier” effect, especially by preventinginterpenetration of the coating layer and the reinforced matrix in thefinal sheet, and also give said sheet fireproofing, waterproofing andthermal and/or acoustic insulation properties.

The structures are in various forms, namely yarns or yarn assemblies(meshes, wovens), films, veils, sheets, panels, foams, etc.

They may consist entirely or partly of polyethylene, polypropylene,polyester, such as polyethylene terephthalate (PET) and polybutyleneterephthalate (PBT), polyamides, polyacrylics, polyurethane, polyester,glass or a metal, and include fillers (talc, calcium carbonate, balsa,wood, cork), adhesives and fire retardants.

The structures have a thickness that may vary widely depending on thematerial used—from 50 micrometers in the case of veils, films andsheets, to several centimeters, in the case of panels. Preferably, thethickness of the structures varies from 0.5 to 2 mm.

The present invention also relates to an installation for implementingthe process, this installation comprising:

-   -   a) at least one device for feeding at least one web of        continuous yarns;    -   b) at least one powder coating device;    -   c) at least one device for heating the powder-coated web; and    -   d) at least one device for compressing, and optionally cooling,        the web.

The installation according to the invention may also include at leastone cutting device and/or at least one collecting device for thecomposite sheet.

The sheets obtained by the process of the invention are inexpensive, asthey are produced continuously. The are formed from a matrix, withinwhich reinforcing filaments are embedded, protected by a coating forminga uniform topcoat, of attractive appearance, which may receivedecorative patterns and inscriptions in the form of paint, varnish orstickers.

If the topcoat is of attractive appearance, especially a uniform, flatand smooth surface without a “emarking” effect, this is primarilybecause the reinforcing yarns are continuous and can be distributed soas to be approximately parallel to the plane of the web during thecompression step. Such a level of performance is not achieved withchopped yarns, particularly short chopped yarns, as they all do not liein the plane of the web under the compression effect, some of themretaining an orientation perpendicular to said plane. In the end, thesurface of the sheet bristles with protuberances, in the form of smallspikes, due to the yarns that protrude therefrom.

The sheets generally have a thickness of 1 to 10 mm, preferably 1 to 6mm, are easy to cut and exhibit good mechanical properties, inparticular good impact (stone-chip, hailstone) resistance. The sheetsobtained are also rigid, but may have, where appropriate, sufficientflexibility to be able to be collected and stored in wound form. Theymay also be used for the thermoforming and molding of parts made ofcomposites.

The composite sheet thus obtained may be used as such or be combinedwith other flexible or rigid products, especially in order to formsandwich panels having an improved strength/weight ratio. The rigidproduct may be in the form of wooden (balsa, chipboard) boards or ofthermoplastic or thermosetting foam, or else have a cellular structure,for example of the honeycomb type, based on aluminum, paper orpolypropylene. The manufacture of the panel is generally carried out bybonding the composite sheet to at least one side of the aforementionedstructure by suitable means, preferably by adhesive bonding. Thefoam-based panels may be obtained from a sheet of foam cut to thedesired dimensions, i.e. be extruded directly on the composite sheet andthen calendered. The thickness of the panels may vary from 2 to 100 mm,preferably from 10 to 50 mm.

The composite sheets and the panels formed from these sheets are moreparticularly intended to form walls used in the transport field (truckbodies, trailers, caravans, camping cars) or the building field(cladding, lightweight construction partitions).

The composite sheets have the advantage of being able to be weldedwithout external addition of material, and are capable of being molded,especially by thermoforming. Furthermore, it is easy to repair thecoating when it has been damaged, simply by depositing the coatingpowder, optionally dispersed in a liquid or in mastic form, and thenheating it. They may also be easily recycled in the form of granules orsmall pieces, for injection molding or compression molding.

BRIEF DESCRIPTION OF THE DRAWING FIGS.

Other advantages are given in the following drawings that illustrate theinvention:

FIG. 1 shows a schematic view of an installation for implementing theinvention in its simplest embodiment; and

FIG. 2 shows a schematic view of an installation for implementing theinvention according to the preferred embodiment.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows schematically a composite sheet production line whichcomprises, upstream, at least one reel (1) of a woven made fromintermingled yarns. The woven (2) paid out from this reel passes over aturn roll (3) and a forwarding roll (4), allowing the tension in the webto be reduced, and then beneath a powder coating device (5) composed ofa grooved roll (5) connected to the base of a reservoir (7) filled withthe coating powder, which distributes the powder over the surface of thewoven.

The powder-coated woven is then heated by infrared radiation panels (8),without being in contact with them, to a temperature high enough to meltthe organic material contained in the yarns and the organic material ofthe powder.

The woven thus heated passes between press rolls (9) which compress themelted organic materials with a force of about 5 kN to 50 kN per meterof width, and then passes over a cooling table (10).

On leaving the table (10), the cooled, rigid, composite strip (11) iscut continuously to the desired dimensions, by the blades (12) of anautomatic shear (not shown), into the form of sheets (13).

In a variant, the yarns are combined into tows that are continuouslysprayed onto the conveyor belt by means of an air ejector (not shown)that moves transversely relative to said strip, in a reciprocatingmotion, in order to form a mat (or web of looped yarns).

FIG. 2 shows schematically an installation for manufacturing a compositesheet according to the preferred embodiment of the invention.

In this embodiment, two wovens (15, 16) of intermingled yarns are paidout from the reels (17, 18) and pass over forwarding rolls (19, 20)before coming together on the conveyor belt (21).

Installed downstream of the reels (17, 18) are two rolls (22, 23) of asurface veil. The veils (24, 25) paid out from the rolls are applied bymeans of the turn rolls (26, 27) to the wovens (15, 16).

A powder coating device (28), comprising a grooved roll (29) connectedto a reservoir (30) containing the coating powder, is installeddownstream of the conveyor belt (21) and above the woven/veilscombination. According to a variant, a second powder coating device (31)may be installed beneath the combination, in order to apply the powderto the underside. This device is composed here of a nozzle (32) forspraying powder preheated by hot air.

The powder-coated woven/veils combination is introduced into a flatlaminating press (33). This press essentially comprises two continuousbelts (34, 35) moved by a set of rollers (36, 37), a heating zone (38),a water-circulation cooling zone (39) and press rolls (40) between whichthe combination is compressed and driven. In the first zone (38), thecombination is heated by plates (41) to a temperature allowing thefilaments of organic material and the powder to melt, the rolls (40)helping both to distribute the molten material uniformly within thecombination and to compact the wovens (15, 16). In the second zone (39),the combination, cooled by the plates (42), is set and consolidated.

What is obtained at the exit of the press (33) is a rigid strip that iswound onto a mandrel (43). Each side of the strip has a uniform andsmooth surface.

In a variant, it is possible to obtain thicker composite sheets byintroducing either a structure comprising an organic matrix andreinforcing yarns, for example in the form of continuous or choppedyarns, one or more wovens, one or more knits or a composite sheet, forexample of the same nature as the aforementioned strip, or a differentstructure, for example foam or cellular panels (44) deposited betweenthe wovens (15, 16) . The panels (44) are placed edge to edge on theconveyor belt (21).

When the thickness of the strip is large and does not allow it to becollected in the form of a reel, it is cut into panels, for example by acircular saw mounted on a follower carriage (not shown).

In another variant, the wovens (15, 16) are replaced with two strips(11) collected in the form of reels produced in the installation of FIG.1.

The following examples illustrate the process according to the inventionand the products obtained by this process.

EXAMPLE 1

The installation described in FIG. 1 was used to manufacture a compositesheet 1.5 m in width and 1.5 mm in thickness, consisting of 60% glass byweight and 40% polypropylene by weight.

Assemblies of continuous yarns, 750 g/m² in weight and 1.5 m in width,comprising, as warp and as weft, intermingled yarns formed from 1870-texintermingled rovings containing 60% glass by weight and 40%polypropylene by weight, were used, the yarns being bound together inthe weft direction by stitching-knitting with a polypropylene bindingyarn.

Two assemblies coming from two reels were superposed on the conveyorbelt and a powder of a polyolefin-based thermoplastic alloy (Plascoat®Talisman sold by Plascoat) was applied to the top side of the assemblyin an amount of 500 g/m². The assembly, running at a speed of 1.5m/minute, was heated between the infrared radiation panels (length: 1 m;temperature: 200° C.) and then passed between the rolls (diameter: 300mm; temperature: 40° C.; nip: 1.5 mm) of the calender.

The composite sheet obtained had a thickness of 1.5 mm and the surfacewas coated with a uniform, white and glossy coating layer 0.5 mm inthickness.

EXAMPLE 2

The installation of FIG. 2 was used.

A “jet fluid”-bonded 70 g/m² polyester veil (reference NLC 10/701 soldby PGI) was deposited on two 745 g/m² wovens formed from 1870 texintermingled rovings containing 60% glass by weight and 40%polypropylene by weight, bulk-colored black, in a 2×2 twill, 1.5 m inwidth, and the powder of thermoplastic alloy of example 1 was applied inan amount of 500 g/m². The assembly was introduced into a double beltpress comprising a heated zone at 200 °C., a two-roll calender(pressure: 1.5 bar (0.15 MPa)) and a cooling zone at 20° C. The pressoperated at a speed of 2 meters per minute.

A sheet 1.5 mm in thickness comprising a uniform glossy coating layer,white in color, was obtained.

EXAMPLE 3

The conditions of example 1 were used. A 50 g/m² glass veil wasdeposited on a 1485 g/m² woven formed from 1870 tex interminged rovingscontaining 60% glass by weight and 40% polypropylene by weight, in a 2×2twill with sides of 1.5 m, and the powder of thermoplastic alloy ofexample 1 was applied in an amount of 500 g/m².

The assembly, running at a speed of 1.5 m/min, was heated between theinfrared radiation panels (temperature: 220° C.) and then passed intothe calender.

The composite sheet obtained had a thickness of 1.5 mm. It was cut upand heated to 220° C. for 1 minute in an infrared oven, it was thentransferred into a press, consisting of a rectangular mold and acountermold regulated to 60° C., and subjected to a 40 bar (4 MPa)pressure for 1 minute.

After demolding, a box 150 mm in width, 200 mm in length and 20 mm inheight, having a uniform coating and no material distribution defect,was obtained.

EXAMPLE 4

An installation as described in FIG. 2 was used to continuously formsandwich panels 1.5 m in width, 2.4 m in length and 22.5 mm inthickness, consisting of a polyurethane foam coated with compositesheets consisting of 60% glass by weight and 40% polypropylene byweight.

Polyurethane foam panels (length: 1.55 m; width: 1.2 m; thickness: 20mm; density: 100 kg/m³; reference: SPF 100, sold by SAITEC) werejuxtaposed on the conveyor.

During displacement, the panels were coated on their top side andunderside with a 1485 tex, 4×4 twill woven, consisting of yarns ofintermingled rovings consisting of 60% glass by weight and 40%polypropylene by weight, followed by a fluid-jet-bonded 70 g/m²polyester veil (NLC 10/701 sold by PGI).

The powder coating devices delivered 500 g/m² of thermoplastic powder(Plascoat® Talisman, sold by Plascoat) on each side of the assembly. Thetemperature of the powder sprayed onto the underside was about 180° C.

In the PTFE-coated glass-cloth belt press, the first zone had a lengthof 1 m and the temperature was about 210° C., the second zone 4 m inlength was maintained at about 20° C. and the calender was composed oftwo rolls 400 mm in diameter, each bearing on the assembly with a forceof 2 kN. The calender nip was 22 mm.

The composite panel was continuously output at a speed of 0.7 m/min andwas then cut using a circular saw into panels 1.5 m in width and 2.4 min length.

The composite strips coating each side of the panels had a void contentof less than 3% and a uniform coating layer white in color.

EXAMPLE 5

The conditions were those of example 4, but modified in that the panelshad a width of 2.9 m and a thickness of 80 mm, and a double steel beltpress, comprising a heated zone 3 m in length and a cold zone of thesame length, exerting a pressure of 2 bar (0.2 MPa) was used, with nocalender between the two zones.

Composite panels 2.9 m in width, 12 m in length and 82.5 mm in thicknesswere thus formed.

EXAMPLE 6

The installation described in FIG. 2 was used to manufacture panels witha polypropylene cellular structure 2.9 m in width, 12 m in length and52.5 mm in thickness, said panels being coated with composite sheetsconsisting of 60% glass by weight and 40% black bulk-coloredpolypropylene by weight.

The core structures consisted of honeycomb-type cellular panels made ofpolypropylene (length: 2.95 m; width: 1.2 m; thickness: 50 mm; density:80 kg/m³) deposited in a contiguous manner on the conveyor.

During their displacement, the top side and underside were coated with acomposite sheet obtained under the conditions of example 3.

The temperature of the hot first zone of the belt press was about 210°C., that of the second zone was about 20° C. and the calender, whose nipwas 52 mm, exerted a pressure of 2 bar (0.2 MPa) on the assembly.

The composite panel was continuously output at a speed of 2 m/min andthen was cut up into rectangles.

EXAMPLE 7

An installation as described in FIG. 2, which included a foam extrusionand calendering device located upstream of the conveyor, was used tocontinuously form a composite sheet 2.9 m in width and 16 mm inthickness, consisting of an expanded polypropylene foam reinforced withglass yarns and coated with composite sheets consisting of 60% glass byweight and 40% polypropylene by weight.

The core foam was formed in a sheet die (not shown) by extrusion from apolypropylene compound containing 10% by weight of chopped glass fibersless than 1 mm in length, said foam being deposited on the conveyor. Atthe die exit, the foam had a thickness of 14 mm, a width of 2.95 m and adensity of 300 kg/m³.

The top side and underside of the foam were coated downstream with a1485 g/m² woven of intermingled rovings containing 60% glass by weightand 40% polypropylene by weight, in a 4×4 twill, and then with afluid-jet-bonded 70 g/m² polyester veil (NLC 10 sold by PGI).

The powder coating devices delivered 600 g/m² of thermoplastic powder(Plascoat® PPA 571 HES sold by Plascoat) onto each side of the assembly.The temperature of the powder sprayed onto the underside was about 160°C.

The press was a steel belt press comprising a first zone 3 m in lengthat about 220° C., a second zone of the same length at about 20° C. and acalender composed of two rolls exerting a pressure of 5 bar (0.5 MPa) onthe assembly. The press nip was set at 16 mm.

The composite sheet was output continuously at a speed of 2 m/min andthen cut up into panels.

The coating on the sheet thus obtained was of excellent quality: inparticular, it had an attractive glossy appearance. This is explained bythe fact that the foam continued to expand under the effect of the heatin the first zone of the belt and that the high pressure of the pressenabled the coating layer to be properly consolidated.

EXAMPLE 8

The conditions used were those of example 2, but modified in that 745g/m² wovens of glass yarns (60% by weight) preimpregnated with athermosetting epoxy resin (40% by weight) taken to.the stage B of cure.

The double belt press was heated to 180° C. and operated at 1 m/min.

A sheet 1.5 mm in thickness, including a glossy uniform coating layer,white in color, was obtained.

EXAMPLE 9 Comparative Example

The conditions used were those of example 1, but modified in that thecoating powder was deposited on the web of yarns in an amount of 390g/m².

The coating on the composite sheet thus formed was not uniform and lefta glimpse of the weft of the woven owing to transparency at severalplaces.

1. A process for manufacturing composite sheets, comprising the stepsof: continuously depositing a web of continuous yarns on a movingsubstrate, the web comprising at least one first organic material and atleast one reinforcing material; depositing a powder of a second organicmaterial on at least one surface of said web; heating the web coatedwith the powder to a temperature sufficient to melt the powder into asmooth surface layer and melt said first organic material to form amatrix within which the reinforcing material is embedded; compressingand cooling the web to form a composite strip formed of said matrixembedded with said reinforcing material and said smooth surface layerpositioned on an external surface thereof; and cutting the strip in theform of sheets or winding the strip on a rotating support.
 2. Theprocess as claimed in claim 1, wherein the powder is selected from thegroup consisting of particles of a thermoplastic material and particlesof a thermosetting material.
 3. The process as claimed in claim 2,wherein the thermoplastic material is selected from polyolefins,polyamides, polyesters and PVC.
 4. The process as claimed in claim 2,wherein the thermosetting material is selected from epoxies, polyesters,polyurethanes and phenolic compounds.
 5. The process as claimed in claim2, wherein the web comprises between 20 and 90%, by weight ofreinforcing material.
 6. The process as claimed in claim 5, wherein thereinforcing material is glass, carbon or aramid.
 7. The process asclaimed in claim 6, wherein the web comprises at least 50% by weight ofintermingled yarns of glass filaments and of filaments of athermoplastic organic material capable of forming a matrix.
 8. Theprocess as claimed in claim 7, wherein the web is exclusively in theform of wovens or of continuous non-interlaced yarns.
 9. The process asclaimed in claim 8, wherein the powder is deposited on the web in anamount sufficient to produce a smooth surface layer with a thickness ofbetween 0.3 and 1 mm.
 10. The process as claimed in claim 1, whereinsaid web includes hybrid yarns formed of thermoplastic organic filamentsand glass filaments.
 11. The process of claim 1, wherein said compositestrip has a width of approximately 1.5 meters.
 12. A process formanufacturing composite sheets at least partly formed from intermingledyarns, comprising the steps of: continuously depositing a web of yarns,in the form of a mat of continuous yarns, the web being formed at leastpartly from intermingled yarns formed of filaments of a thermoplasticorganic material and glass filaments intimately mixed; depositing on atleast one side of said web a powder of an organic material having afilm-forming capability in an amount sufficient to form a smooth surfaceunder the action of heat; heating the web coated with the powder to atemperature high enough to convert the web of yarns into a matrix withinwhich the glass filaments are embedded and to melt the powder into atopcoat having a smooth surface; and compressing and cooling the web toform a composite strip.
 13. The process of claim 12, wherein the powderof an organic material has an opacity sufficient to make the glassfilaments in the matrix invisible.
 14. The process of claim 12, whereinthe step of depositing a powder further comprises depositing a powder onboth sides of said web.
 15. The process of claim 12, wherein theintermingled yarns comprise a woven material.
 16. The process of claim12, wherein the topcoat has a thickness between 0.3-1 mm.
 17. Theprocess of claim 12, wherein the filaments of a thermoplastic organicmaterial and the powder of an organic material comprise the samematerial.
 18. The process of claim 17, wherein the filaments of athermoplastic material and the powder of an organic material comprisepolypropylene.
 19. The process of claim 12, wherein the web iscompressed with a force of about 5 kN to 50 kN per meter of width. 20.The process of claim 12, further comprising the step of preventinginterpenetration of the topcoat and the matrix by introducing anintermediate layer there between.
 21. A process for manufacturingcomposite sheets, comprising the steps of: continuously depositing a webof continuous yarns on a moving substrate, said web comprising at leastone first organic material and at least one reinforcing material;depositing at least one intermediate structure on at least one surfaceof said web; depositing a powder of a second organic material on saidintermediate structure; heating said web to a temperature sufficient tomelt said powder into a smooth surface layer and melt said first organicmaterial to form a matrix within which said reinforcing material isembedded; compressing and cooling said web to form a composite strip;and cutting the strip in the form of sheets or winding the strip on arotating support.
 22. The process as claimed in claim 21, wherein saidat least one intermediate structure is selected from yarns or yarnassemblies, films, veils, sheets, panels and foams.
 23. The process asclaimed in claim 21, wherein said web includes hybrid yarns formed ofthermoplastic organic filaments and glass filaments.